CN115282952A - Catalyst for preparing cyanamide by catalyzing urea decomposition - Google Patents

Catalyst for preparing cyanamide by catalyzing urea decomposition Download PDF

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CN115282952A
CN115282952A CN202211040834.6A CN202211040834A CN115282952A CN 115282952 A CN115282952 A CN 115282952A CN 202211040834 A CN202211040834 A CN 202211040834A CN 115282952 A CN115282952 A CN 115282952A
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catalyst
acid
urea
cyanamide
reactor
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CN115282952B (en
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吕树祥
姚月
董利兵
许晓安
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Tianjin University of Science and Technology
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J21/00—Catalysts comprising the elements, oxides, or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium, or hafnium
    • B01J21/02—Boron or aluminium; Oxides or hydroxides thereof
    • B01J21/04—Alumina
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J21/00—Catalysts comprising the elements, oxides, or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium, or hafnium
    • B01J21/02—Boron or aluminium; Oxides or hydroxides thereof
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J27/00—Catalysts comprising the elements or compounds of halogens, sulfur, selenium, tellurium, phosphorus or nitrogen; Catalysts comprising carbon compounds
    • B01J27/02—Sulfur, selenium or tellurium; Compounds thereof
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J27/00—Catalysts comprising the elements or compounds of halogens, sulfur, selenium, tellurium, phosphorus or nitrogen; Catalysts comprising carbon compounds
    • B01J27/14—Phosphorus; Compounds thereof
    • B01J27/16—Phosphorus; Compounds thereof containing oxygen, i.e. acids, anhydrides and their derivates with N, S, B or halogens without carriers or on carriers based on C, Si, Al or Zr; also salts of Si, Al and Zr
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J27/00—Catalysts comprising the elements or compounds of halogens, sulfur, selenium, tellurium, phosphorus or nitrogen; Catalysts comprising carbon compounds
    • B01J27/24—Nitrogen compounds
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J31/00—Catalysts comprising hydrides, coordination complexes or organic compounds
    • B01J31/02—Catalysts comprising hydrides, coordination complexes or organic compounds containing organic compounds or metal hydrides
    • B01J31/04—Catalysts comprising hydrides, coordination complexes or organic compounds containing organic compounds or metal hydrides containing carboxylic acids or their salts
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/02—Impregnation, coating or precipitation
    • B01J37/0201—Impregnation
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/08—Heat treatment
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/08—Heat treatment
    • B01J37/082—Decomposition and pyrolysis
    • B01J37/088—Decomposition of a metal salt
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/30—Ion-exchange
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01C—AMMONIA; CYANOGEN; COMPOUNDS THEREOF
    • C01C3/00—Cyanogen; Compounds thereof
    • C01C3/16—Cyanamide; Salts thereof

Abstract

The invention provides a catalyst for preparing cyanamide by catalyzing urea decomposition, which is prepared by the following steps: calcining pseudo-boehmite at high temperature to prepare a catalyst carrier; adding a catalyst carrier into an acid solution, and uniformly mixing to obtain mixed slurry; loading acid in the mixed slurry on the catalyst carrier, and drying to obtain a precursor; and roasting the precursor at high temperature to obtain the catalyst. The invention also provides a method for preparing a crude product of cyanamide by using the catalyst to catalyze urea decomposition. The catalyst has more active sites, and particularly can greatly improve the urea conversion rate and the cyanamide selectivity in a specific fixed bed reactor; in addition, the catalyst prepared by the method is easy to obtain raw materials, and the preparation method is simple, easy to control, low in cost and good in economical efficiency.

Description

Catalyst for preparing cyanamide by catalyzing urea decomposition
The technical field is as follows:
the invention relates to the field of novel catalytic system design and application, in particular to a catalyst for preparing cyanamide by catalyzing urea decomposition.
Background art:
the cyanamide is an important chemical raw material, an organic chemical intermediate and a very important medical raw material, can also be used as an intermediate of a pesticide product to produce a pesticide, and has stable market demand and good prospect.
The existing methods for preparing cyanamide mainly comprise five methods: the lime nitrogen process, the ammonia process, the urea process, the hydrocyanic acid process, and the urea decomposition process. The lime nitrogen method, the ammonia method, the urea method and the hydrocyanic acid method all have obvious disadvantages: the lime nitrogen method has high energy consumption, complex production process, large equipment investment and serious pollution, and domestic and foreign manufacturers are more and more strictly limited by environmental regulations, and the process is to be eliminated and replaced inevitably; the ammonia process, the urea process and the hydrocyanic acid process have the same problem of serious pollution, and have the defects of low yield, high industrialization difficulty and the like. Further, among the above methods, there have been no reports on industrialization of each method other than the lime nitrogen method.
The method for preparing the cyanamide by decomposing the urea accords with the atom economy principle, has low energy consumption, little pollution and low cost, and has better prospect for realizing industrialized large-scale production. In addition, the method can fundamentally avoid the problems that the product produced by the traditional method for preparing the cyanamide by taking the lime nitrogen as the raw material contains more free calcium carbide and the like. The research and application of the production process for preparing the cyanamide by decomposing the urea become new hotspots gradually by combining the advantages of nitrogen fertilizer production in China. Although the method for preparing the cyanamide by decomposing the urea has a plurality of potential advantages, the method still has the outstanding problems of low conversion rate, low selectivity of the cyanamide and the like in the urea decomposition process and needs to be solved urgently.
The invention content is as follows:
in view of the above problems, it is an object of the present invention to provide a catalyst for preparing cyanamide by catalytic decomposition of urea, which can significantly improve the conversion rate and the selectivity of cyanamide in the urea decomposition process under suitable conditions.
The catalyst for preparing cyanamide by catalyzing urea to decompose is prepared by the following steps:
1) Calcining pseudoboehmite (namely alumina monohydrate and pseudoboehmite) at 500-1100 ℃ for 2-5 h to prepare a catalyst carrier;
2) Adding the catalyst carrier into an acid solution, and uniformly mixing to obtain mixed slurry;
3) Loading acid in the mixed slurry on the catalyst carrier by adopting an impregnation method or an ion exchange method, and drying to obtain a precursor;
4) And roasting the precursor at 550 ℃ for 5 hours to obtain the catalyst.
Further, in the step 3), the loading amount of the acid in the mixed slurry on the catalyst carrier is 0.1 to 10wt%.
Preferably, the acid solution in step 2) is a solution obtained by mixing any one or more of hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, acetic acid, boric acid or citric acid and then diluting with deionized water.
On the basis, the invention provides a process method for preparing a crude product of cyanamide by using the catalyst to catalyze urea decomposition, which comprises the following steps:
1) Sequentially filling a proper amount of glass beads, quartz sand and a catalyst into a fixed bed reactor according to a certain sequence, and stacking the glass beads, the quartz sand, the catalyst and the catalyst in the reactor from bottom to top to form a glass bead-quartz sand-catalyst-glass bead bed layer;
2) Adding urea into a reactor, and continuously reacting for a period of time at 400-650 ℃ in an ammonia atmosphere;
3) And products at the outlet of the reactor are condensed and cooled to obtain products.
Further, in the step 2), the feeding rate of the urea into the reactor is 0.01-5 g/min, the residence time of reactants is 0.1-2.5 s, and the continuous reaction time is 30min.
Further, in the step 2), the urea is directly added into the reactor in a solid form or is added into the reactor after being heated to a molten state at the temperature of 130-170 ℃.
Further, when urea is added into the reactor in a molten state, the solid, liquid and gas three-phase characteristics of the process for preparing the crude cyanamide product respectively comprise: the "solid" is the catalyst, the "liquid" is the molten urea, and the "gas" is ammonia.
The crude cyanamide prepared by the process method can be used for testing the urea conversion rate and the selectivity of cyanamide and other byproducts, so that the solid-liquid-gas three-phase characteristics of the process method for preparing the crude cyanamide can also be used for testing the process method.
Compared with the prior art, the invention has the technical effects that:
1) The catalyst prepared by the method has more active sites, and particularly can greatly improve the urea conversion rate and the cyanamide selectivity in a specific fixed bed reactor; wherein, the urea conversion rate is not less than 95 percent, and the cyanamide selectivity is not less than 55 percent.
2) The catalyst prepared by the method is easy to obtain raw materials, and the preparation method is simple, easy to control, low in cost and good in economical efficiency.
Description of the drawings:
figure 1 is an XRD characterization of the fresh catalyst prepared in example 7 before use and after 7 consecutive uses.
The specific implementation mode is as follows:
the technical solution of the present invention will be described in detail with reference to examples.
1. Preparing a catalyst:
example 1
1) Roasting 15g of pseudo-boehmite in a muffle furnace at the high temperature of 550 ℃ for 5 hours to prepare a catalyst carrier;
2) Dissolving 0.12g of boric acid in 30mL of deionized water, and uniformly stirring to obtain an acid solution; adding 12g of catalyst carrier into an acid solution, and stirring to uniformly mix the catalyst carrier and the acid solution to obtain mixed slurry;
3) Loading acid in the mixed slurry on the catalyst carrier by adopting an impregnation method, and drying to obtain a precursor; wherein the acid loading on the catalyst support is 1wt%;
4) And roasting the precursor at the high temperature of 550 ℃ for 5 hours to obtain the catalyst.
Example 2
1) Roasting 15g of pseudo-boehmite in a muffle furnace at the high temperature of 550 ℃ for 5 hours to prepare a catalyst carrier;
2) Dissolving 0.12g of citric acid in 30mL of deionized water, and uniformly stirring to obtain an acid solution; adding 12g of catalyst carrier into an acid solution, and stirring to uniformly mix to obtain mixed slurry;
3) Loading acid in the mixed slurry on the catalyst carrier by adopting an impregnation method, and drying to obtain a precursor; wherein the acid loading on the catalyst support is 1wt%;
4) And roasting the precursor at the high temperature of 550 ℃ for 5 hours to obtain the catalyst.
Example 3
1) Roasting 15g of pseudo-boehmite in a muffle furnace at the high temperature of 550 ℃ for 5 hours to prepare a catalyst carrier;
2) Dissolving 0.12g of nitric acid in 30mL of deionized water, and uniformly stirring to obtain an acid solution; adding 12g of catalyst carrier into an acid solution, and stirring to uniformly mix the catalyst carrier and the acid solution to obtain mixed slurry;
3) Loading acid in the mixed slurry on the catalyst carrier by adopting an impregnation method, and drying to obtain a precursor; wherein the acid loading on the catalyst support is 1wt%;
4) And roasting the precursor at the high temperature of 550 ℃ for 5 hours to obtain the catalyst.
Example 4
1) Roasting 15g of pseudo-boehmite in a muffle furnace at the high temperature of 550 ℃ for 5 hours to prepare a catalyst carrier;
2) Dissolving 0.12g of sulfuric acid in 30mL of deionized water, and uniformly stirring to obtain an acid solution; adding 12g of catalyst carrier into an acid solution, and stirring to uniformly mix the catalyst carrier and the acid solution to obtain mixed slurry;
3) Loading acid in the mixed slurry on the catalyst carrier by adopting an impregnation method, and drying to obtain a precursor; wherein the acid loading on the catalyst support is 1wt%;
4) And roasting the precursor at the high temperature of 550 ℃ for 5 hours to obtain the catalyst.
Example 5
1) Roasting 15g of pseudo-boehmite in a muffle furnace at the high temperature of 550 ℃ for 5 hours to prepare a catalyst carrier;
2) Dissolving 0.12g of phosphoric acid in 30mL of deionized water, and uniformly stirring to obtain an acid solution; adding 12g of catalyst carrier into an acid solution, and stirring to uniformly mix the catalyst carrier and the acid solution to obtain mixed slurry;
3) Loading acid in the mixed slurry on the catalyst carrier by adopting an impregnation method, and drying to obtain a precursor; wherein the acid loading on the catalyst support is 1wt%;
4) And roasting the precursor at the high temperature of 550 ℃ for 5 hours to obtain the catalyst.
Example 6
1) Roasting 15g of pseudo-boehmite in a muffle furnace at the high temperature of 550 ℃ for 5 hours to prepare a catalyst carrier;
2) Dissolving 0.36g of sulfuric acid in 30mL of deionized water, and uniformly stirring to obtain an acid solution; adding 12g of catalyst carrier into an acid solution, and stirring to uniformly mix the catalyst carrier and the acid solution to obtain mixed slurry;
3) Loading acid in the mixed slurry on the catalyst carrier by adopting an impregnation method, and drying to obtain a precursor; wherein the acid loading on the catalyst support is 3wt%;
4) And roasting the precursor at the high temperature of 550 ℃ for 5 hours to obtain the catalyst.
Example 7
1) Roasting 15g of pseudo-boehmite in a muffle furnace at the high temperature of 550 ℃ for 5 hours to prepare a catalyst carrier;
2) Dissolving 0.36g of acetic acid in 30mL of deionized water, and uniformly stirring to obtain an acid solution; adding 12g of catalyst carrier into an acid solution, and stirring to uniformly mix the catalyst carrier and the acid solution to obtain mixed slurry;
3) Loading acid in the mixed slurry on the catalyst carrier by adopting an impregnation method, and drying to obtain a precursor; wherein the acid loading on the catalyst support is 3wt%;
4) And roasting the precursor at the high temperature of 550 ℃ for 5 hours to obtain the catalyst.
Example 8
1) Roasting 15g of pseudo-boehmite in a muffle furnace at the high temperature of 550 ℃ for 5 hours to prepare a catalyst carrier;
2) Dissolving 0.6g of citric acid in 30mL of deionized water, and uniformly stirring to obtain an acid solution; adding 12g of catalyst carrier into an acid solution, and stirring to uniformly mix the catalyst carrier and the acid solution to obtain mixed slurry;
3) Loading acid in the mixed slurry onto the catalyst carrier by adopting an impregnation method, and drying to obtain a precursor; wherein the acid loading on the catalyst support is 5wt%;
4) And roasting the precursor at the high temperature of 550 ℃ for 5 hours to obtain the catalyst.
2. Preparation of crude cyanamide:
1) Proper amount of glass beads, quartz sand and catalyst are successively filled into a fixed bed reactor according to a certain order, and a glass bead-quartz sand-catalyst-glass bead bed layer is formed by stacking from bottom to top in the reactor. The following specific operations are preferred: sequentially filling the following components into the fixed bed reactor from bottom to top: 75g of glass beads, 10g of quartz sand, 8mL of a catalyst (prepared in example 7), and 8g of glass beads.
2) Adding urea into a reactor at a feeding rate of 1g/min, and continuously reacting for 30min at 550 ℃ under an ammonia atmosphere, wherein the residence time of reactants is 0.5s.
The urea can be directly added into the reactor in a solid form through a solid feeder, or can be added into the reactor after being heated to a molten state at the temperature of 130-170 ℃; in this example, urea is added to the reactor after it is heated to a molten state.
3) And (3) condensing and cooling a product at the outlet of the reactor through a serpentine condenser pipe to obtain a product crystal (namely a crude cyanamide product).
3. Process test (including test of urea conversion, cyanamide and selectivity of by-products):
the obtained product crystals were subjected to constant volume measurement in a volumetric flask and then detected. The concentration of the cyanamide in the reaction product is determined by referring to the test method and the inspection rule of HG/T5537-2019 'Industrial cyanamide', and other byproducts are analyzed by using a high performance liquid chromatograph.
The urea conversion and the selectivity of products such as cyanamide are shown in table 1: it can be seen from the table that under appropriate conditions, the catalyst of the present invention can increase the urea conversion rate to more than 95%, and the cyanamide selectivity to more than 55%.
TABLE 1 Urea conversion and selectivity to catalytic decomposition products
Figure BDA0003820384960000071
The process method for preparing the crude cyanamide product and the solid-liquid-gas three-phase characteristics for testing the process method respectively comprise the following steps: the "solid" is the catalyst, the "liquid" is the urea in molten state, and the "gas" is ammonia.
4. Catalyst stability test
The catalyst prepared in example 7 was selected and analyzed by XRD testing before use and after 7 consecutive uses, respectively.
The XRD characteristics of the catalyst before and after use are shown in figure 1, and as can be seen from figure 1, the XRD characteristic peaks of the catalyst before and after use are not changed, which indicates that the catalyst has excellent stability.
The foregoing embodiments and description have been presented only to illustrate the principles and preferred embodiments of the invention, and various changes and modifications may be made therein without departing from the spirit and scope of the invention as hereinafter claimed.

Claims (9)

1. A catalyst for preparing cyanamide by catalyzing urea decomposition is characterized by being prepared by the following steps:
1) Calcining pseudo-boehmite at 500-1100 ℃ for 2-5 h to prepare a catalyst carrier;
2) Adding the catalyst carrier into an acid solution, and uniformly mixing to obtain mixed slurry;
3) Loading acid in the mixed slurry on the catalyst carrier by adopting an impregnation method or an ion exchange method, and drying to obtain a precursor;
4) And roasting the precursor at 550 ℃ for 5 hours to obtain the catalyst.
2. The catalyst of claim 1, wherein: in the step 3), the loading amount of the acid in the mixed slurry on the catalyst carrier is 0.1 to 10wt%.
3. The catalyst according to claim 1 or 2, characterized in that: the acid solution in the step 2) is a solution obtained by mixing any one or more of hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, acetic acid, boric acid or citric acid and then diluting with deionized water.
4. A process for preparing crude cyanamide by using the catalyst of claim 1 to catalyze urea decomposition, which is characterized by comprising the following steps:
1) Sequentially filling a proper amount of glass beads, quartz sand and a catalyst into a fixed bed reactor according to a certain sequence, and stacking the glass beads, the quartz sand, the catalyst and the catalyst in the reactor from bottom to top to form a glass bead-quartz sand-catalyst-glass bead bed layer;
2) Adding urea into a reactor, and continuously reacting for a period of time at 400-650 ℃ in an ammonia atmosphere;
3) And condensing and cooling the product at the outlet of the reactor to obtain a product.
5. The process for preparing crude cyanamide according to claim 4, wherein: in the step 2), the feeding rate of the urea into the reactor is 0.01-5 g/min, the residence time of reactants is 0.1-2.5 s, and the continuous reaction time is 30min.
6. The process for preparing crude cyanamide according to claim 4 or 5, wherein: in step 2), urea is directly added to the reactor in solid form.
7. The process for preparing crude cyanamide according to claim 4 or 5, wherein: in the step 2), the urea is heated to a molten state at 130-170 ℃ before being added into the reactor.
8. The process for preparing crude cyanamide of claim 7, which comprises the following steps: the "solid" is the catalyst, the "liquid" is the molten urea, and the "gas" is ammonia.
9. The method for testing the solid, liquid and gas three-phase characteristics of the process for preparing the crude cyanamide of claim 7 is characterized by respectively comprising the following steps: the "solid" is the catalyst, the "liquid" is the molten urea, and the "gas" is ammonia.
CN202211040834.6A 2022-08-29 Catalyst for preparing cyanamide by catalyzing urea decomposition Active CN115282952B (en)

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Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0827127A (en) * 1994-07-20 1996-01-30 Mitsui Toatsu Chem Inc Production of melamine
CA2431037A1 (en) * 2000-12-15 2002-06-20 Agrolinz Melamin Gmbh Modified inorganic particles
CN102728400A (en) * 2011-04-15 2012-10-17 中国石油化工股份有限公司 Catalyst for preparing cyanamide by dehydrating urea and its preparation method
CN109999813A (en) * 2019-03-15 2019-07-12 上海大学 A kind of methane catalytic decomposition catalyst for preparing hydrogen and preparation method thereof
CN112275281A (en) * 2020-10-15 2021-01-29 中国石油大学(华东) Fischer-Tropsch synthetic oil noble metal hydrogenation catalyst and preparation method thereof
CN114751844A (en) * 2021-05-31 2022-07-15 天津科技大学 Process method for preparing cyanamide by catalyzing dehydration of urea

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0827127A (en) * 1994-07-20 1996-01-30 Mitsui Toatsu Chem Inc Production of melamine
CA2431037A1 (en) * 2000-12-15 2002-06-20 Agrolinz Melamin Gmbh Modified inorganic particles
CN102728400A (en) * 2011-04-15 2012-10-17 中国石油化工股份有限公司 Catalyst for preparing cyanamide by dehydrating urea and its preparation method
CN109999813A (en) * 2019-03-15 2019-07-12 上海大学 A kind of methane catalytic decomposition catalyst for preparing hydrogen and preparation method thereof
CN112275281A (en) * 2020-10-15 2021-01-29 中国石油大学(华东) Fischer-Tropsch synthetic oil noble metal hydrogenation catalyst and preparation method thereof
CN114751844A (en) * 2021-05-31 2022-07-15 天津科技大学 Process method for preparing cyanamide by catalyzing dehydration of urea

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Title
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